During assembly and packaging, multiple semiconductor dice are usually placed onto a single carrier in array form and processed in bulk for increasing productivity. After electrical connections are made between the dice and the carrier, the dice, together with the electrical connections should be encapsulated with molding compound to protect them from the external environment. Thereafter, the resulting packages that encapsulate the dice have to be cut to separate them from one another.
The separation of the electronic packages is typically conducted by sawing. After sawing, the packages need to be further processed, for example by washing, drying, inspection and finally offloading. One sawing approach is disclosed in U.S. Pat. No. 6,165,232 entitled “Method and Apparatus for Securely Holding a Substrate During Dicing”, which approach may be conveniently referred to as a nesting jig sawing approach. The nesting jig saw has been one popular type of sawing method implemented in the industry. A nest having a grid arrangement is put onto a saw jig before sawing, and a substrate to be sawn is supported on the nest. After sawing, an upper nest is placed onto the sawn packages. Thereafter, all the sawn packages and the lower and upper nests are carried together to other processing stations by a pick arm. Subsequent processes, such as pick and place and sorting according to inspection results, are performed in conjunction with the “nested” packages. The sorted good packages will then be offloaded to plastic tubes, trays or canisters, while bad packages are offloaded to reject bins or reject/rework trays.
However, the handling of sawn packages in this way is complicated as nests (both upper and lower) are required during sawing as well as during the washing and drying processes. The nests can be complex to fabricate and to use when the package size becomes small, say 3 mm×3 mm, and the density of the packages on the carrier becomes high. Hence, high costs may be incurred for conversion kits to cater for different package dimensions and for subsequent handling. For the same reason, setup and conversion time are increased.
Another approach is disclosed in U.S. Pat. No. 6,446,354 entitled “Handler System for Cutting a Semiconductor Package Device”. It discloses an alternative method of handling packages after sawing, without the use of a nesting jig saw. Instead, the sawn packages are either collected by a transfer carrier, or collected by a vacuum head. Subsequent processes are similar to those performed in other handlers, such as washing and drying, inspection of the molded surfaces for markings and lead surface inspection.
In this approach, the substrate is sawn on a saw jig and held by vacuum only during the process of sawing. After sawing, packages are picked by vacuum and transferred for washing and drying while the packages are still held by the vacuum head. After cleaning and drying, the packages are placed onto a hot plate with an array of small vacuum holes for secondary drying and lead or ball inspection. Thereafter, half of the packages are put onto a turntable with a buffer plate on top (on which pockets are arranged in alternating format), while the other half are put onto the second half of the buffer plate. The buffer plate can rotate if required in order to rotate the packages to a preferred orientation before being picked up by dual offload pick arms for offloading.
A shortcoming of the above process is that a complicated buffer plate is required in order to accommodate the packages effectively, since some form of guiding wall has to be provided for each pocket. Therefore, more expensive fabrication methods are required. The buffer plate would be even more complicated and expensive when the packages decrease in size (to say, 3 mm×3 mm) and the density of packages is higher. There is also potential that the sawn packages might not sit properly (e.g., they might be tilted) in the pockets of the buffer plate due to improper placement. On the one hand, the clearance between the pocket walls and the packages cannot be too large, or the subsequent offloading process cannot accurately put the packages into a tray or a tube. On the other hand, too small a clearance can lead to unstable positioning of the packages on the buffer plates. This contradictory phenomenon is more obvious when handling smaller packages (e.g., 2×2 mm and 3×3 mm).
Yet another non-nesting approach is disclosed in U.S. Pat. No. 6,655,045 entitled “Apparatus and Method for Pick and Place Handling”. Instead of sawn packages being picked up by vacuum, a gang transfer arm conveys all the sawn packages to various processing stations with a “sliding” approach. The sawn packages are slid by a rinsing carrier from the saw jig to the rinsing platform and by a drying carrier for the drying process on the same platform. The packages are subsequently moved row by row onto a transfer track where the packages are separated at the track end. Inspection will then be conducted before offloading the packages to a tray, tube, reject bin or canister according to the inspection result.
A disadvantage of the said method is that the conversion kit to cater for different packages is complicated, especially for the rinsing and drying carriers. As a result, the conversion kit can be costly. The set-up and conversion are difficult as quite a lot of leveling adjustments are required in order to effectively slide the sawn packages across various processing stations on the same platform. Furthermore, only top inspection can be provided as the bottom surfaces of the packages are supported on the platform.